Smart cards, or data transaction cards, for carrying out data transactions are in wide use and well known per se. A concise introduction to the nomenclature and principal features of smart cards, also called data to transaction cards, is found in a paper by Gilles Lisimaque, presented at the 27th International SAMPE Technical Conference, on Oct. 9-12, 1995.
The term "smart card" as used below refers to a data card with the geometrical dimensions of an ISO 7816 standard contact card: about 86.times.54.times.0.8 mm and having either a contact or contactless interface or a combined contact/contactless interface as described, for example, in our co-pending Israel Patent Application No. 119943 filed on Dec. 31, 1997.
Smart cards have historically been used to perform passive tasks only which are not time-related, mainly for identification, authentication, and data collection duties, by contact and/or contactless communication. However, there are many situations wherein it is necessary to perform different actions according to a sequence of time-related operations. For example, rather than merely condition a smart card's response on passive data stored therein as has been done so far, it would be advantageous to allow the smart card to respond to data as it is received in accordance with the received data.
However, current smart cards lack the autonomous processing and communication capability needed for controlling industrial processes, usually involving time and performance monitoring adaptable to various situations. Thus for smart cards to be considered for manufacturing tasks and to become cost effective, there is required an improvement in those features related to processing, transaction and response to sensors. In order that the smart card may remain compact, the enhanced processing facility must not unduly increase its power consumption and this has tended to militate against the use of smart cards for such applications.
U.S. Pat. No. 5,491,672 in the name of R. Ferris describes a system using RF tags to monitor a watchman's performance. Ferris discloses a system with the use of a portable interrogation time clock unit carried by a watchman for receiving a passive answer when coming in range of an RF tag or card located at a site to be visited. The unit carried by the watchman is bulky and employs radio frequency communication with relatively high power consumption. Consequently, such a system lacks the convenience and portability associated with smart cards. Furthermore, the task of the static RF tags or cards is entirely passive and the system is not designed to deliver a warning or a reminder if a required task is neglected.
Another attempt to create an advanced monitoring system is found in U.S. Pat. No. 5,682,142 to Loosmore et al., describing a network of fixed stations and movable tags communicating with each other. Loosmore does not provide a system of autonomous stations and smart cards but rather requires that the component devices are interconnected in a network formation. This allows mutual communication between all nodes in the network, both fixed and moving. It does not appear that such a system is constrained by low energy requirements which are less relevant to node tags than to smart cards. Furthermore, data transfer via wireless transceiver which is inherently power-consuming.
Although smart cards are inherently well suited for portable, low-power applications, known smart cards suffer from low range communication, usually in the order of only 30 to 50 cm. This is acceptable for passive systems wherein a moveable transponder is brought into close proximity with a fixed station as is typically the case when data in the smart card is to be read by the station. However, it militates against the use of smart cards for process monitoring where relatively long range communication between the station and transponder is required in the order of several meters.